Finally bought a MEP-831a

[AfghanVeteran2010]

I filled it up with oil, I couldn't source any John Deere Break in oil locally. I used Rotella T 10W-30 figure Ill use this since I had it on hand. I adjusted the valve last night, decided I would see if I had compression by turning fly wheel by hand. Turns out I messed up the valve job, there is quite a leak on the exhaust side. Since I have the studs for exhaust removed I can create a seal with the palm of my hand. When I place my hand over it I get a good seal good enough to make a squeaking noise from the air escaping under my hand.

So it apparent I didn't do a good enough job on valves, the valve grinding compound that I used is 120 grit. I think that was the mistake and using lead off of pencil to check the seal of valves. I see that 440 grit is need for finish. I am just happy that I caught this before placing it back into unit and running it. I plan to pull head and regrind valves starting with course then fine grit then check seals.



When I do break this unit in I'm not worried about saving fuel by running it at the minimum hours. I'll probably run it for 5 hrs then change oil/filter, 10 hrs change oil/filter, then normal intervals. I wont consider this set mission ready till I put 50 hours on it after this tear down, just my personal opinion. I don't want to be worried about unit when its running, I swear I'm paranoid when I have a gen set running that is new to me.

 

[DieselAddict]

Thats a bummer about the valve sealing. For auto heads we test them before putting them back on the engine by putting some acetone in the combustion chambers and look for leaks. That isn't practical here since the head doesn't have a combustion chamber per say.

Glad you caught it before staring it up.

 

[rustystud]

Just remember, "just because your paranoid doesn't mean that their "not" out to get you" !!!

 

[AfghanVeteran2010]

Thats a bummer about the valve sealing. For auto heads we test them before putting them back on the engine by putting some acetone in the combustion chambers and look for leaks. That isn't practical here since the head doesn't have a combustion chamber per say.

Might be able to test intake and exhaust by filling the ports up, just have to plug up oil hole on intake side. Would rubbing alcohol suffice?

 

[DieselAddict]

Sure m

 

[AfghanVeteran2010]

Turns out leak is also on intake side as well, I relapped them and the leak is still present on both sides. I think I'm going to order a new head and valves and send them off to be lapped. The finest grinding lapping compound I can find locally is 280 grit is this fine enough?

 

[DieselAddict]

Before you do that take it to a machine shop and have them look at it. They may get you going for just a few bucks.

 

[AfghanVeteran2010]

I droped it off at shop, ill know in a few days.

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[DieselAddict]

Cool. I hope they fix you up so you are ready to go.

 

[rustystud]

Before you do that take it to a machine shop and have them look at it. They may get you going for just a few bucks.

Your valves and seats looked fine, so a little touch-up from the machine shop should be all they need.

 

[AfghanVeteran2010]

Just picked up head from machine shop, turns out there is nothing wrong with it. Holds a 7 at vacuum with no spring, they said lapping job looked really good. They mentioned that the valve lashing maybe incorrect or the tappet may not be seated correctly on cam shaft. The tappets looked good when I put it back together. The rockers arms moved freely when in compression stroke. I'm going to take closer look at rockers when in motion

 

[DieselAddict]

Great news.

One of the things I personally do for a first start is I set the valves a few thousands looser than spec. I don't run the engine very long on its first start. Maybe 1-2 minutes. I will then go back and check valve lash and set it to spec.

 

[AfghanVeteran2010]

Okay Ill give that a try.

 

[AfghanVeteran2010]

Here's the first run under load, sure smoked a lot. I ran it for 2 mins then set lash. then applied load video is about a min after load was on. Is this to be expected?

https://youtu.be/YAWDTXE4bWs

 

[DieselAddict]

Not unusual. How long did you let it run loaded? The smoke should have tapered off as the rings wear in. Did you set the gaps on the rings?

 

[AfghanVeteran2010]

been running it for 20 mins and the engine just quits dies. rings were set to manual spec; (end gaps staggered 120° apart). Unless you talking about something different. smoke has not changed any. loaded at 1200 watts

 

[AfghanVeteran2010]

lossed total compression, reason was found. see picture

Once engine cools Im going to inspect push rods and set to tighter valve lashing. was set to 0.15 mm range (0.10 to 0.15 mm)
Going to set it to .10mm this time.
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[AfghanVeteran2010]

Perhaps my injection timing is incorrect it was set to 17 degrees before TDC. per TM 16 to 18. But the yanmar manual states 13-15. Is there a reason for the difference? Improper timing might explain the constant black smoke. Tomorrow morning ill adjust the valves and maybe timing depending of what is recommend.

 

[DieselAddict]

Edit - defer to post below.

 

[Dewie38]

Go by the TM, these engines were set up differently by Yanmar for this use.